Explain the plasma membrane.
a fluid lipid bilayer embedded with proteins and a small amount of carbohydrates.
Why are membranes important?
- they are selectively permeable
- can maintain differences in ion concentrations inside and outside the cell
- enables the cell to respond to changes in the cells environment.
What is the definition of integral, transmembrane and peripheral proteins?
- Integral = are embedded in the lipid bilayer
- Transmembrane = extend through the membrane.
- Peripheral = are more common intracellularly
Name the main functions of the lipid bilayer.
- forms the basic structure of the membrane
- the hydrophobic interior serves as a barrier
- enables the cell to change shape.
What are the two methods of unassisted membrane transport?
- down a concentration gradient
2. along an electrical gradient
What is the definition of osmolarity?
the concentration of osmotically active particles present in a solution.
What is the definition of tonicity?
the effect a solution has on cell volume
Explain carrier mediated transport.
the substance binds to a specific carrier which undergoes a conformational change which transports the substance.
According to Frick’s Law of Diffusion, what influences the rat of net diffusion across the membrane?
- magnitude of the concentration gradient
- surface area of the membrane
- lipid solubility
- molecular weight
- distance of diffusion needed.
Explain 3 specialised cell juctions
Desmosomes; adhering junctions that anchor cells together
Tight junctions; join the lateral edges of cells
Gap junctions; allows the movement of charge carrying ions
How do ions permeate the membrane?
if there is a difference in changre and that creates an electrical gradient between the ICF and the ECF, then th
What is carrier mediated transport affected by?
specificity, saturation and competition.
What is the difference between primary and secondary active transport?
Primary transport - energy is directly required to move a substance against its concentration gradient.
Secondary Transport - energy is required but it is not used directly to produce ‘uphill’ movement
Secondary Active Transport occurs by one of two mechanisms, explain them.
- Symport (co-transport)
2. Antiport (exchange or counter transport)
